At the age of twenty-six Gnaeus Pompeius is considered such a brilliant general that his own troops, after a campaign in Africa in 80 BC, call him Pompeius Magnus - Pompeius the Great - in a flattering echo of Alexander the Great. In English he is known more simply as Pompey.

Pompey's military reputation continues to grow and in 67 BC he is entrusted with an important mission - to rid the Mediterranean of the pirates who are terrorising coastal regions and ruining Rome's trade. They are said to have as many as 1000 ships in their combined fleets. In view of the evident difficulty of the task, the senate gives Pompey three years to complete it.

He takes three months. He annihilates the entire pirate fleet in a brilliantly planned operation, astonishing in an age when long-range communication is difficult. To prevent his prey from constantly slipping out of reach, Pompey divides the Mediterranean and Black Sea into thirteen regions, each with its own commander. A carefully coordinated operation over the entire area soon mops up the pirate vessels.

This success brings Pompey, in 66 BC, an even more important command. He is to take charge of the Roman legions in Asia Minor. The entire eastern Mediterranean, from Anatolia through Syria to Palestine, is in a state of unrest and anarchy. His task is to bring it under control.

Again he achieves his purpose with great skill. Anatolia is subdued. Syria is annexed in 64 BC as a Roman province. Phoenicia and Palestine are soon merged with it, though Jerusalem only falls to him after a three-month siege.

Throughout the region Pompey establishes administrative systems which will preserve peace in the coming years. They will also bring in vast new quantities of annual tax. When Pompey enjoys his triumph in Rome, in September of 61 BC, the quantity of gold and bullion dragged along in his procession is greater than any general has brought home before. It is sufficient to provide a generous bounty for his soldiers and still leave much for the treasury.

On bringing his victorious fleet and army into Brindisi, late in 62 BC, Pompey has dismissed his legions in the correct manner - it is illegal for Roman generals to bring their armies on to Italian soil. But there is, as always on such occasions, an implicit understanding between the legionaries and their leader; he will use his influence to provide plots of land on which they can support themselves.

For two years Pompey fails to fulfil this obligation, owing to political obstruction from opponents in Rome. The situation brings him into a natural alliance with two other powerful but frustrated men - Crassus, a one-time political colleague of his, and the up-and-coming Julius Caesar.

The first triumvirate: 60-53 BC

Pompey, Crassus and Caesar all have grievances against the senate. Caesar, elected consul for the coming year, 59 BC, could normally expect a provincial governorship; instead he has been given the supervision of Italy's forests and cattle trails. Pompey has not been allowed the land which he needs for the disbanded veterans of his army. Crassus has been frustrated in a profitable tax-collecting venture in Asia.

The three men form, in 60 BC, what is now known as the first triumvirate. To cement the link, Pompey marries in 59 Caesar's only child, Julia (though he is older than her father). With equal cynicism, selective rioting by Pompey's veterans is used to persuade the senators to change their minds.

In the circumstances, they do so.

Land is found for the veterans. The business problems of Crassus are resolved. And instead of forests and cattle trails, Caesar finds himself in charge of Rome's two northern provinces - Cisalpine and Transalpine Gaul.

Caesar's new provinces provide him with rich opportunities: to recruit soldiers far away from Rome who will be loyal to him alone; to achieve new conquests which will impress the public at home; and to amass large personal funds by looting conquered territories. Meanwhile Pompey stays in Rome, hoping to further his own interests by political means.

These two are now the most powerful men in the republic. As allies they are unbeatable. The underlying question is how long it will be before they emerge, in truer colours, as rivals.

Caesar and Pompey: 54-48 BC

During the first few years of Caesar's absence from Rome the triumvirate retains its cohesion. Part of the reason is that the marriage between Pompey and Caesar's daughter proves surprisingly happy. But Julia dies in 54, after giving birth to a daughter. In 53 Crassus is killed campaigning in Asia, at Carrhae. There is little now to mask the inevitable rivalry between Pompey and Caesar.

The senators in Rome, alarmed by Caesar's successes in Gaul, incline towards Pompey as their best protection. In an attempt to clip Caesar's wings, the senate instructs him, in December of the year 50 BC, to give up his command of Gaul and to return to Rome as a private citizen.

When Caesar receives the senate's message, he is in the southern part of his territory, in Cisalpine Gaul. The boundary between this province and central Italy is a small river, the Rubicon, flowing east into the Adriatic just north of modern Rimini. Caesar's response is immediate. He marches his army south towards Rome, crossing the river on 10 January 49.

Quite apart from his disregard of the senate's instructions, it is against the law for any commander to bring a Roman army outside the province to which he and it are assigned. In crossing the Rubicon, Caesar consciously and irrevocably launches a civil war.

Pompey escapes the immediate danger by embarking a large army in a fleet of ships and retreating across the Adriatic to Greece. Caesar pursues him there and eventually defeats him at Pharsalus, in the summer of 48 BC.

Pompey flees again, this time to Egypt. But his presence is regarded by a faction in the Ptolemaic court as a likely source of trouble. He is stabbed to death as he steps ashore.